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Encyclopedia of Astrobiology


Distal impact ejecta, Microkrystite, Microtektite


Spherules are distal deposits of meteorite impacts. They are spherical droplets that can form in two ways: as silicate splash particles of ejected impact melt and as condensates from the rock-vapor plume. Glassy spherules that do not contain any crystallites are called microtektites (Glass 1990). These often contain vesicles and are commonly originated as melt spherules. Crystal-bearing spherules, in contrast, are typical to have originated from vapor condensates and are termed microkrystites (Glass and Bohor 1988). Spherules can be less than a hundred micrometers to a few millimeters in diameter. Spherules may be deposited globally or in strewn fields which radiate from the crater.


Spherule beds are sedimentary layers that are composed entirely of spherules or, if reworked, may contain detrital material. Pure spherule beds can be up to a few decimeters thick. The impact-related origin can be recognized by...

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References and Further Reading

  • Abramov O, Mojzsis SJ (2009) Microbial habitability of the Hadean Earth during the late heavy bombardment. Nature, 459(7245):419–422

    Google Scholar 

  • Chao ECT, Boreman JA, Minkin JA, James OB, Desborough JA (1970) Lunar glasses of impact origin: physical and chemical characteristics and geologic implications. J Geophys Res 75(35):7445–7479

    Article  ADS  Google Scholar 

  • Cockell CS, Bland PA (2005) The evolutionary and ecological benefits of asteroid and comet impacts. Trends Ecol Evol 20(4):175–179

    Article  Google Scholar 

  • Cockell CS, Lee P, Osinski G, Horneck G, Broady P (2002) Impact-induced microbial endolithic habitats. Meteorit Planet Sci 37(10):1287–1298

    Article  ADS  Google Scholar 

  • Glass BP (1990) Tektites and microtektites: key facts and inferences. Tectonophysics 171(1):393–404

    Google Scholar 

  • Glass BP, Burns CA (1988) Microkrystites-A new term for impact-produced glassy spherules containing primary crystallites. In Lunar and Planetary Science Conference Proceedings 18:455–458

    Google Scholar 

  • Glass BP, Simonson BM (2012) Distal Impact Ejecta Layers: A Record of Large Impacts in Sedimentary Deposits. Springer Science & Business Media

    Google Scholar 

  • Kring DA (2003) Environmental consequences of impact cratering events as a function of ambient conditions on Earth. Astrobiology 3(1):133–152

    Article  ADS  Google Scholar 

  • Kyte FT, Shukolyukov A, Lugmair GW, Lowe DR, Byerly GR (2003) Early Archean spherule beds: Chromium isotopes confirm origin through multiple impacts of projectiles of carbonaceous chondrite type. Geology 31(3):283–286

    Article  ADS  Google Scholar 

  • Kyte FT, Zhou L, Lowe DR (1992) Noble metal abundances in an Early Archean impact deposit. Geochimica et Cosmochimica Acta 56(3):1365–1372

    Google Scholar 

  • Lowe DR, Byerly GR (1986) Early Archean silicate spherules of probable impact origin, South Africa and Western Australia. Geology 14(1):83–86

    Article  ADS  Google Scholar 

  • Lowe DR, Byerly GR, Asaro F,Kyte F J (1989) Geological and geochemical record of 3400-million-year-old terrestrial meteorite impacts. Science 245(4921): 959–962

    Google Scholar 

  • Lowe DR, Byerly GR, Kyte FT, Shukolyukov A, Asaro F, Krull A (2003) Spherule beds 3.47–3.24 billion years old in the Barberton Greenstone Belt, South Africa: a record of large meteorite impacts and their influence on early crustal and biological evolution. Astrobiology 3(1):7–48

    Article  ADS  Google Scholar 

  • Melosh HJ, Vickery AM (1991) Melt droplet formation in energetic impact events. Nature 350:494–497.

    Google Scholar 

  • Mojzsis S, Abramov O (2009) Microbial habitability of the Hadean Earth during the late heavy bombardment. Nature 459:419–422

    Article  ADS  Google Scholar 

  • Pierazzo E, Artemieva N (2012) Local and global environmental effects of impacts on earth. Elements 8(1):55–60

    Article  Google Scholar 

  • Sleep NS, Zahnle K, Kasting JF, Morowitz H (1989) Annihilation of ecosystems by large asteroid impacts on the early Earth. Nature 342:139–142

    Article  ADS  Google Scholar 

  • Shukolyukov A, Lugmair G (1998) Isotopic evidence for the Cretaceous-Tertiary impactor and its type. Science 282(5390):927–930

    Google Scholar 

  • Shukolyukov A, Kyte FT, Lugmair GW, Lowe DR, Byerly GR (2000) The oldest impact deposits on Earth—First confirmation of an extraterrestrial component. Impacts and the early Earth:99-115. Springer Berlin Heidelberg

    Google Scholar 

  • Shukolyukov A, Lugmair GW (2001) Extraterrestrial matter on Earth: Evidence from the Cr isotopes. In Catastrophic events and mass extinctions: Impacts and beyond 1:3041

    Google Scholar 

  • Toon OB, Zahnle K, Morrison D, Turco RP, Covey C (1997) Environmental perturbations caused by the impacts of asteroids and comets. Rev Geophys 35(1):41–78

    Article  ADS  Google Scholar 

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Correspondence to Nadja Drabon .

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Drabon, N. (2014). Spherules. In: Amils, R., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg.

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